No example I'm afraid (I'm a nanny not a childminder), but have helped other childminders do letters in the past.
You need to set things out Very Clearly. Make it as easy as possible for them to say Yes.
List every child involved including their full date of birth and age at start of variation, such as: Harry 14-Mar-03 (4yrs 1 month)
Indicate clearly the sibling relationships, so group children by family. Indicate clearly which child(ren) is NEW.
At the moment, I don't really understand what you are wanting exactly, as it isn't clear.
Your son is 4.
You currently mind a 4 year old in addition.
Your friend has 4 year old twins, 2 year old and baby?
You do not currently childmind for your friend?
Looks to me as that could be 5 under 5's.
How is your current registration phrased (knowing exact wording helps)? Is your son for example included or excluded from the under 5's figure? If attending 10 educational sessions then he can be excluded, but if attending 9 or less sessions, he's in ratio.
Feel free to contact me direct if you like, as to help you it does help me to know some more information which you may feel is too personal to post.
Google NannyNick to get my website which contains contact details, or send a CAT.